1. Field of the Invention
The invention relates generally to systems and methods for transferring fluids from subsea components to surface vessels. More particularly, the invention relates to systems and methods for transferring fluids from a subsea free-standing riser to a surface vessel.
2. Background of the Technology
Free-standing riser (FSR) systems are used during production and completion operations to transfer fluids from a subsea well to a surface vessel. Conventional free-standing risers include a rigid vertical conduit formed by an arrangement of steel pipes secured to the sea floor at its lower end with a foundation. The upper portion of the free-standing riser is positioned subsea, below the wave zone, and typically comprises an upper riser assembly. One or more tensioning buoys are coupled to the upper riser assembly to support the weight of the riser and maintain the riser in tension. Flexible flowlines or “jumpers” connect the upper riser assembly to a surface vessel, thereby enabling the flow of produced hydrocarbons from the riser to the vessel. The combination of a rigid riser section which extends vertically from the seafloor to an upper end below the wave zone, and a flexible section comprised of flexible flowlines extending from the top of the rigid section to a floating vessel on the surface is often referred to as “hybrid” risers.
Some conventional free-standing riser systems include connect/disconnect systems that enable a surface vessel to connect to and disconnect from the jumpers. For example, a surface vessel may be disconnected from a free-standing riser and moved to avoid a floating iceberg, hurricane, etc. However, such conventional connect/disconnect systems are tailored to a particular type of surface vessel and/or require specific hardware that may not be available on all vessels. Moreover, some conventional connect/disconnect systems take a relatively long period of time to connect and/or disconnect from the free-standing riser, which may be problematic in an emergency situation where a very quick disconnection is desirable without damaging hardware or discharging hydrocarbons into the surrounding sea.
Accordingly, there remains a need in the art for efficient fluid transfer systems (FTS) and methods for transferring hydrocarbon fluids between a subsea system such as a free-standing riser and a surface vessel. Such systems and methods would be particularly well-received if they provided a relatively quick connect/disconnect capability from the surface and could be operated with a variety of different vessels.